Method of controlling oscillations of vehicle bodies



Dec. 18, 1934. J. M. NALLE 1,984,539

METHOD OF CONTROLLING OSCILLATI ONS OF VEHICLE BODIES Original Filed Jan. 21, 1929 3 Sheets-Sheet 1 TN V EN TOR.

A TTORNEY J. M. NALLE Dec. 18, 1934.

METHOD OF CONTROLLING OSCITJIJATTONS OF VEHICLE BODIES Original Filed Jan. 21, 1929 3 Sheets-Sheet 2 m "V w a WWW m ATTORNEY Patented Dec. 18, 1934 METHOD OF CONTROLLING OSCILLATIONS OF VEHICLE BODIES John M. Nalle, Fairfield,

Conn, assignor to American Chain Company, Inc., a corporation of New York 1 Original application January 21, 1929, Serial No. r 333,758. Divided and this application June 10,

1931, Serial No. 543,273 l 8 Claims.

This application is a division of my co-pend ing application for Shock absorber, Ser. No. 333,758, filed January 21, 1929.

My invention relates to improvements in methods of controlling oscillations of vehicle bodies,

and one of itsobjects is to control such oscillations in both directions away from the normal relative position of the body and chassis.

Another object is to so retard the spring at vent the axle of thevehicle from sharply striking the vehicle frame.

Other objects of my invention will in some casesbe readily apparent and in others be pointed out specifically in the following description of a preferred embodiment of my invention, while the novelty and scope of the invention Will thereafter be pointed out in the claims.

In the accompanying drawings:

Fig. -1 is 'a' view in longitudinal section of my shock absorber, the section being taken on the line 1-1 of Fig. 3, part of the linkage for connecting the piston to an axle being shown in full;

5 Fig. 2 is a view, in longitudinal section, taken on the line 2-2 of Fig. 1;

Fig. 3 is a view, in transverse section, showing the shock absorber attached to a portion of a vehicle frame, the section being taken on the line 3-3 of Fig. 1;

Fig. 4 is an end view of the piston, looking in the direction of the arrows 4--4 of Fig. 1;

Fig. 5 is an indicator card illustrating typical resistance-travel curves obtained with my shock absorber at a certain setting thereof;

Fig. 6 is a view in perspective of the piston; and

Figs. '7 to 11 are diagrams illustrating pressure-travel curves obtainable with various Ti throttles.

My shock absorber comprises a main body provided with a hollow cylinder portion 11, the latter being closed at each end by means oi caps 12'screwed thereon. Above this cylinder the body is formed with a chamber 13 which communicates with the bore of the cylinder and is closed at the top by means of a cover 14. The chamber 13 and the cylinder 11 are adapted to receive a quantity of oil or other suitable damping fluid which may be introduced therein through a port 15, the latter being normally closed by a screw plug 16.

Fitted within the cylinder 11 is a double ended piston which divides the cylinder into two .working chambers, 11a and 11b. The piston the end of its compression stroke as to pre- 20 is flattened at the top, intermediate its ends, to form a recess 21 communicating with the chamb er'13, and a similar recess 22 is formed in the underside of the piston. Extending ver tically through the piston from the recess 21 to the recess 22, is a slot 23 of rectangular form. This slot is adapted to receive a shoe 24 formed with an arcuate socket 26 running transversely therethrough of somewhat more than 180 degrees in extent. This socket is adapted to receive a cylindrical knob 27 formed on the end of a crank arm 28. The crank arm is secured to a shaft 29 which is journaled in bearings 30 and 31 in the body 10 and extends in a plane transverse to the cylinder 11.

As shown in Fig. 3 the shaft 29 projects from the side of the casing 10, and a stuffing box 32 of suitable form is provided to prevent leakage of oil through the bearing 31 and out of the body 10. The projecting end of the shaft 29 has, attached thereto, a crank arm 35, the outer end of which arm is connected by a ball and socket joint to a connecting rod 36. The shock absorber body 10 is provided with pads 37 adapted to be seated against a fixed part 38 of the vehicle frame, being held thereagainst by bolts 39 or other suitable means. The rod 36 is connected to the axle (not shown) of the vehicle, and since the axle is connected to the vehicle frame through a vehicle spring in the usual manner, compression and expansion of said spring will a result in corresponding oscillation of the crank 28 and reciprocation of the piston 20.

As shown in Fig. 3 the shaft 29 has secured thereon an indicator arm 40, by which it is possible to determine whether the piston 20 is normally in central position in the cylinder 11. The crank arm may be adjusted on the shaft 29 so that this desired central position is. obtained. The arm 40 is notched at its lower end and a center pin 41 in the casing 10 serves to indicate by its position with respect to said notch when the piston is in central position.

As the crank arm 28 oscillates, the shoe 24 will move up and down within the slot 23, be cause the socket 26 has an angular extent of more than 180 degrees, causing the shoe 24 to cling to the knob 27 on the free end of the crank arm. In order to prevent trapping or pumping of oil due to the vertical movements of the shoe, ducts 21a and 212) are provided in the piston,

end of the knob 27 is flattened, as indicated at 43, leaving a slight space for oil which serves to keep the knob and socket lubricated. In assembling the piston, the shoe 24 is applied to the knob by sliding it transversely thereon, after which the crank 28 with the shoe connected thereto may be inserted in the slot 23.

As shown in Figs. 2 and '3 the cylinder 11 is formed with a seat44 at one side to receive a throttle bar' 45. The latter extends practically the full length of the cylinder and is secured to 1 spectively, tothrottle the flow of liquid 'into and Communication out of the working chambers. is provided between therecess 49 and the recess 22 by way of openings 53, so that fluid entering the recess 49 from either working chamber may flow out into the body of oil stored in the supply chamber 13.

On the side opposite the slot 48 the piston is formed with a duct 54 running from end to end of the piston. This duct is centrally contracted to form an annular valve seat 55, in which a valve 56 is fitted to slide. The valve 56 is normally held in central position by opposed compression springs 57a and 57b. These springs fit upon stems 58a and 58b projecting from opposite ends of the valve 56. The springs bear at one end against the body of the valve and are secured to the piston at their opposite ends by means of pins 59a and 59?) respectively. The body of valve 56 is conically tapered to a smaller diameter at each side of its central transverse plane so as to graduate the size of the opening formed as the valve moves ofi its seat in either direction. The duct 54 provides communication between the chamber 11a and chamber 111) and the valve 56 will open to permit exchange of fluid between these chambers when the pressure in either one of them overbalances the pressure in'the otherto such an extent as to move the valve clear of the valve seat 55.

I also employ a cushioning device at one end of the piston, which comprises a spring-pressed cushion plunger 60. The plunger and an opposed plunger 61 are fitted to slide in a bore 62 formed in the piston. The bore extends from the righthand face of the piston, as shown in Figs. 1 and2, to the slot 23 in which slides the shoe 24. The plungers 60 and 61 are preferably cup-shaped, with their concave faces inward to receive a compression spring 64. This spring presses the cushion plunger 60 against a strap 65 so that it lies flush with the end of the piston 20. At the same time the plunger 61 is pressed againstthe shoe 24 and serves to take up any slack between said shoe and the slot 23, thus overcoming any tendency for the shoe to knock and 11b filled with oil, refill ports 66a and 66b are provided which lead from the recess 22 into said chambers respectively. Each of these ports is furnished with a check valve opening towards the working chamber. The check valves are indicated in Fig. l at 67a and 67b respectively. 1

The operation of the shock absorber will now be explained. Hereinafter I shall use the term compression stroke, when applied to the spring or axle, as denoting the whole upward movement of the spring or axle whether above, below, or through normal, while the term expansion stroke will denote the corresponding downward movement. This should not be confused with the compression produced by the piston which takes place in one chamber or the other on movement of said piston in either direction. The shock absorber "as illustrated in Fig. 1 is shown in normal position with the piston centrally located in the cylinder. Starting from normal position, as the piston20 moves toward the right it displaces oil from chamber 11a and at the same time causes the wall 50 to ride over the notch 46. At first the passage through said notch, under the wall, will widen, until the wall has been centered over the notch, after which it will gradually close as the outer edge of the wall approaches the outer inclined face of the notch. As the piston advances toward the right, the fluid displaced from chamber 11a. escapes under the wall 50 and thence through recess 49 and the ports 53 to the central chamber 13. When the wall 50 coacting with the notch 46 begins to throttle this escape, the

pressure in the chamber 11a will build up at a rate which is determined by the slope of the forward inclined wall of the notch 46, and also by the action of the cushion plunger 60. The spring 64 is relatively light and consequently the cushion will yield and reach the limit of its depression before the pressure in the working chamber has mounted to a high value.

Before the passage under the wall 50 has been entirely closed off, the pressure will be great enough to open the spring controlled valve 56, permitting fluid to flow out of the chamber 11a, through the duct 54, directly into the opposite working chamber 11b. The extent of opening in the duct 54 depends upon the strength of the springs 58a and 58b, and also upon the conical taper of the valve 56. Aside from affording control of the valve opening, the taper oi the valve prevents chattering such as is liable to take place when an ordinary ball valve is used. If the movement of the piston is sufficient the passage through the throttle notch 46 eventually will be entirely out oif and all the fluid in the chamber 11a displaced by the piston will then have to pass out through the duct 54.

While the piston 20 was moving toward the right, the notch 47 was at first gradually closed by the wall 51 and was entirely out oh by said wall before the wall 50 began to throttle the passage of fluid through the notch 46. Thus, while initially a certain amount of fluid was permitted to flow from the chamber 11a directly into the chamber 111) this was soon out 01f, and the only way in which fluid could enter the chamber 11b was by way of the refill port 661). Now, when the piston 20 starts to return toward the left, it will find its progress resisted by the fluid in the working chamber 112?. The only escape for this fluid, assuming that the wall 51 has moved beyond the notch 47 1's by way of the duct 54,"and as the springs controlling the valve 5.6 are set to resist open ingliioi ithe'valve until'a' predetermined high pressure is developed in the chamber 11b, a substantially greater initial resistance will be offered tothe expansion stroke "of the vehicle spring than was offered to its initial compression strokes ."Not until the piston'has moved tar 'en'eugh for the wall 51 to begin to uncover the notch 47 will this pressure be materially relieved andthen'the relief wlllbe controlled bythe shape of the inner inclined face of the notch 47. After the piston has returned to its normal central position and has begun to move past such position, the outer. edge of the wall 5l-wili begin to throttle-thepassage from the chamber. 11b 'tosthe recess 4.9 and pressure will again develop in; the chamber 11b. On return of the pistont'oward the right a heavy pressure will be built up in the chamber 111a because the notch lfiwill then be closed oil by the wall 50. This pressure, however, will not be built upas rapidly as was the heavy pressure in chamber 11b, because of yielding of the cushion plunger 68.

".The diagramFig. 5 illustrates a series of typi cal. resistance travel curves which could be obtainedwitlr my shock absorber. In this diagram measurements parallel to the axis XX' represents stresses developed in the connecting link/and measurements parallel to the axis YY represent movements of the vehicle axle with respect to the body or vice versa. The normal central position of the piston is indicated at O. Movements of the piston toward the right are read upward on the diagram and movements toward the left, downward. Variations of pressure in the chamber 11a are indicated by the lines to the right of axis YY and pressures in the chamber 11b to the left of said axis. Thus, on an initial compression of a vehicle spring the line O-abc indicates the variation of pressure in the chamber 11a with corresponding displacement of the piston. The pressure at first is practically negligible and then begins to rise at a as the notch 46 begins to be throttled. When this throttling becomes excessive the valve 56 begins to act- At about the point I) the notch 46 is entirely closed and the only escape for the oil is by way of the valve 56. The line O--abc represents the pressure curve which would result were the piston not provided with the cushion plunger 60.

In the diagram I have shown a numberof curves in full lines indicated by thereference letters A, B, C, D, E, and F. Each of these is a typical resistance-travel curve obtained by a sustained oscillation of the spring through a chamber drops rapidly to zero.

predetermined range. Thus the curve A represents a cycle of pressures obtained by'oscillating the spring through a maximum range." After thepressure has risen to a maximum in the chamber. lie the piston starts to move in the opposite direction and the pressure in said At the same time pressure will be rapidly built up in the chamber 11b, reaching a maximum at a point d. This'pressure willbe maintained at a fairly constant value even past the point at which the notch '4'? begins to open, because the velocity of the pistonis a factor that must be considered. At the point e'the escape through the notch 4'7 will be sufficient to cause a rapid drop of pressure in chamber llh which will continue even after the piston has moved well past the normal position indicated by the axis X--X'. At some point the throttling of the notch 4712 by the wall 51 will be suflicient to build up pressure again in the chamber 111). Eventually the pres sure will rise sufficiently to open the valve 56 against the spring 59a, the pressure curve reaching a maximumat g.

On thereturn stroke of the piston the pressure curve developed in the fourth quadrant Y'-- O-X would be identical with that developed in the seconol quadrant Y--OX, were it not for the cushion plunger. The full line h--i-a represents the pressure developed if no cushion is present and the broken line h-i'-;i represents the modification caused by the cushion. How ever, the pressure curve in the first quadrant X-.O-Y after the initial stroke would not be materially afiected by the cushion,because there would be sufiicient pressure throughout to keep the cushion plunger fully depressed. Hence, the curve in the first quadrant would be substantially identical with. that in the third quadrant XOY'. H I

The shape of the resistance-travel curve will depend upon the amplitude of movement of the spring. Thus the smallest curve F is practically a straight line curve, with substantially no pressure on movement of the compression stroke of the spring but a slight pressure developed, on the expansion stroke. In other words, as the piston moves through a limited range toward the right in Fig- 2 there will be practically no throttling oi the fluid by the throttle wall 50, but there will be a slight throttling on the return stroke while the inner edge of the wall 51 is un covering the notch 4'7, and because of the velocity of the piston as it passes normal this pressure will continue until the spring has reached the end of its expansion stroke. The curve E diiiers considerably from the curve F because the movement of the piston is sufiicient to bring considerable throttling action into play and the same is true of curves D and C. It will be observed that With the throttles as illustrated, a straight line pressure is provided on movements of the spring away from normal in either direction, in oscillations of magnitudes up to and including that of curve C. In the case of curves B and A, however, the velocity of the piston is such as to materially increase the pressure near the end of its stroke. This increased pressure retards the spring and prevents excessive fiexure thereof.

It must be borne in mind that the diagram shows resistance-travel curvesproduced by sustained oscillations of, the spring and that in actual practice the curves will spiral down to zero as the oscillation of the spring dies down.

The cushion plunger 61 plays an important part in taking care of sudden jolts produced when the vehicle wheels strike an abrupt obstruction at high speed. It is particularly valuable in taking care of jolts produced when the wheel drops into a hole and then is thrown suddenly upward as it strikes the far wall of the hole. Thus, assuming that the piston has dropped to the position It in the diagram and then encounters the far wall of the hole, if no cushion were provided the pressure would mount suddenly in the chamber 11a imparting a severe jolt to the vehicle'frame. With the cushion plunger present, however, the shock is eased ofi, and the pressure follows the curve hz"j.

The cushion plunger 60 may be placed at each end of the piston but preferably is provided only atthat end which is under pressure during the compression stroke of the spring. It is on movements in this .direction that the highest pressures may develop. Thevehicle body moves up and down only at its natural periodicity and theaxle moves downward under limited spring pressure with a harmonic motion due to the natural period of oscillation of the spring in conjunction with the weight of the wheels and axle, but the upward movement of the axle may take place at a much higher rate, depending upon theshape of the obstacle encountered and the speed of travel of the vehicle. In other words, there are known maximum fluid pressures to contend with, insofar as body movements are concerned, but some indefinite ones resulting from the upward axle movements, and by placing the cushion plunger in the right hand end of the piston, as shown in the drawings, abrupt variations of pressure on the compression stroke of the spring are taken care of. The cushion plunger could be placed in the cylinder wall instead of in the piston, if desired.

It will be clear from the foregoing description that I have devised a 'shock'absorber in which retarding resistances are provided in each quadrant of a pressure cycle. The escape of oil from the working chamber is determined by position-controlled throttle means and also by pressure-controlled throttle means; the operation of one of these means overlaps the operation of the other on movements of considerable magnitude. The position-controlled throttling means may be varied by varying the location,-

size and inclination of the notches in the throttle bar, while the pressure-controlled throttling means may be varied by changing the shape of the valve 56 and the strengthoi the springs 58a and 58b. The resistance-travel curve may be further modified by varying the diameter of the cushion plunger and the strength of the spring 64.

In Figs. 7 to 11, inclusive, I have shown various pressure-travel curves, illustrating with each curve the form of throttle with which the curve may be obtained. The curve shown in Fig. 7v is similar to curve A in Fig. 5. That portion of curve which lies in quadrant I is like the portion in quadrant III and similarly in curves in quadrants II and IV are alike. The initial compression curve is indicated by the broken line O-c and the initial expansion curve by the line O--g. This eiIect is produced with a throttle of such form that the piston walls and 51 are positioned alike over the notches 46 and 4'7 when the piston is in normal position.

In Fig. 8 the notch 46 is greatly extended and reaches practically to the center of the recess 49 when the piston is in normal position. As a result of this setting there is little pressure in quadrant IV, but the pressure in quadrant I rises to practically the same amount as in quadrant I of Fig. 7. The curves in quadrants II and III of Fig. 8 are substantially the same as those in the corresponding quadrant of Fig. '7. y

In Fig. 9 the notch 47 is eliminated and the throttle is provided with only a single notch 46 of the same shape as that in Fig. 7. This results in a curve in which the pressure on the expansion stroke is maintained almost constant through quadrants II and III while the curves in quadrants I and IV are similar in general form to those in the corresponding quadrants of The initial expansion stroke indicated by the line O-g differs materially from those in the previous diagrams.

Fig. 10 illustrates a still further modification caused by extending the notch 46 to the left and right. The resultant curve is somewhat like that of Fig. 7 except that the pressure in the first quadrant does not reach so high a value and the pressure in quadrant IV is relieved sooner. Fig. 11 illustrates the result of eliminating notch 47 and cutting away the throttle on the right hand side, so that notch 46 has no confining outer wall but is in the form of a step. This results in a straight line curve of low pressure on the compression stroke with a comparatively heavy compression approximating a straight line curve on the expansion stroke. The initial expansion stroke Og is similar to that in Fig. 9.

The curves given above are used to illustrate the variety of pressure controls obtainable with my improved shock absorber and also. to show that the pressure characteristics in each quadrant may be controlled independently of the characteristics in any'other quadrant. By my improved position-controlled throttle, I control not only the rate at which resistance is applied to the displacement of fluid from. the working chambers in each quadrant, but also the amount of resistance in the quadrant, thus determining the amount of energy'absorbed by each quadrant in the cycle.

It will be understood of course that the curves shown in Figs. 7 to 11 are formed by continuous oscillations of the vehicle spring and that in practice these curves would spiral down to zero as the oscillations of the spring were damped.

In all the diagrams Figs. '2 to. 11, the action of the cushion plunger is eliminated. Obviously these curves would all be modified by the presence of a cushion plunger.

While I have described a preferred embodiment of my invention I do not wish to be limited to the specific structure here illustrated, but I consider myself at liberty to make such changes and variations in form, construction and arrangements of the parts as may be found desirable and as are included within the spirit and scope of my invention, as pointed out in the following claims.

I claim:

1. In the method of retarding oscillations of a spring, the steps which consist in employing the energy of the spring to exert pressure on a body of liquid and force a portion thereof through an orifice, varying the area of the orifice in predetermined relation to successive instantaneous positions of the spring, and modifying the pressure by permitting resilient displacement, without loss, of a portion of the body of liquid.

2. In the method of retarding oscillations of a spring, the steps which consist in employing the energy of the spring to exert pressure on a body of liquid and force a portion thereof through an orifice, varying the area of the orifice in predetermined relation to successive instantaneous positions of the spring, providing steps which consist in unyieldingly constricting.

the discharge of fluid displaced by the piston in predetermined proportion to the successive instantaneous positions of the piston, and yieldingly constricting the discharge when a relatively high fluid pressure has been developed by reason of such position-controlled constriction.

4. In the method of resisting the reciprocation of a piston in a hydraulic shock absorber, the steps which consist in unyieldingly constricting the discharge of fluid displaced by the piston in predetermined direct proportion to the successive instantaneous positions of the piston, and yieldingly constricting the discharge when a relatively high fluid pressure has been developed by reason of such position-controlled constriction, the unyielding and yielding constrictions being so adjusted as to produce a greater resistance to movements of the piston in either direction toward normal than in either direction away from normal.

5. In the method of retarding oscillations of a spring, the steps which consist in employing the energy of the spring to exert a cycle of pressures on a body of liquid and providing individual control of the pressures developed in each quadrant of the cycle.

6. In the method of retarding oscillations of a spring, the steps which consist in employing the energy of the spring to exert a cycle of pressures on a body of liquid and thereby cause displacement of the liquid, applying resistance to such displacement, and varying the rate of application of resistance in each quadrant of the cycle independently of any other quadrant.

7. In the method of retarding oscillations of a spring, the steps which consist in employing the energy of the spring to exert a cycle of pressures on a body of liquid and thereby cause displacement of the liquid, applying resistance to such displacement, and varying the amount of such resistance in each quadrant of the cycle independently of any other quadrant.

8. In the method of retarding oscillations of a spring, the steps Which consist in employing the energy of the spring to exert a cycle of pressures on a body of liquid and thereby cause displacement of the liquid, applying resistance to such displacement, and varying the rate of application and amount of such resistance in each quadrant of the cycle independently of any other quadrant.

JOHN M. NALLE. 

